Evaporators, condensers and systems for separation

Abstract

The current disclosure provides a method to improve the performance of evaporators and condensers by maintaining the vapor velocities on the heat exchange surfaces within a desired range. This is accomplished by providing a constant or tapered narrow gap for vapor flow in the heat exchangers. The shear induced by the vapor over the heat exchanger improves the evaporator performance by disturbing the liquid film flowing over the heat transfer surface. In the condenser, the vapor shear helps to remove the condensate in the form of film and droplets, and also removes the non-condensable gases from the heat transfer surfaces as the vapor condenses out and increases the concentration of the non-condensable gases over the heat transfer surfaces. Parameters identified include minimum gap and the taper angle between the cover plate and heat transfer surface.

What is claimed: 
     
         1 . An evaporator, comprising:
 a flow channel having two open ends, the flow channel comprising a heat transfer plate, optionally two sidewalls, and a cover plate enclosing the flow channel;   a feed liquid inlet at one end of the flow channel;   a feed liquid outlet at the other end of the flow channel;   optionally, a vapor flow inlet at one end of the flow channel; and   a vapor flow outlet at the other end of the flow channel, wherein a gap at the feed liquid outlet between the surface of the heat transfer plate and the surface of the cover plate is in the range of from 1 mm to 200 mm and wherein an angle between the surface of the heat transfer plate and the surface of the cover plate is in the range of from 0.5 to 20 degrees.   
     
     
         2 . The evaporator of  claim 1 , wherein the heat transfer plate has surface features of one or more of fins, grooves, ridges, dimples, microchannels, swirl generators, ripple generators, wave generators, porous surfaces, porous coatings, hydrophilic coatings, hydrophilic surface treatment, biphilic surfaces, nanostructures, capillary flow structures, enhanced evaporation surfaces, and liquid film flow disruptors. 
     
     
         3 . The evaporator of  claim 1 , wherein at least one of the heat transfer plate and the cover plate has a stepped surface to provide the increase in cross-sectional flow area for the vapor. 
     
     
         4 . The evaporator of  claim 1 , wherein the flow channel comprises a cross-sectional area increasing in the vapor flow direction. 
     
     
         5 . The evaporator of  claim 1 , wherein the cover plate is a heat transfer plate. 
     
     
         6 . A condenser, comprising:
 a flow channel having two open ends, the flow channel comprising a heat transfer plate, optionally two sidewalls, and a cover plate enclosing the flow channel;   a vapor inlet at one end of the flow channel; and   a condensed liquid outlet at the other end of the flow channel, wherein a gap at the condensed liquid outlet between the surface of the heat transfer plate and the surface of the cover plate is in the range of from 1 mm to 200 mm and wherein an angle between the surface of the heat transfer plate and the surface of the cover plate is in the range of from 0.5 to 20 degrees.   
     
     
         7 . The condenser of  claim 6 , wherein the heat transfer plate has surface features of one or more of fins, grooves, ridges, dimples, microchannels, swirl generators, ripple generators, wave generators, porous surfaces, porous coatings, hydrophilic coatings, hydrophilic surface treatment, biphilic surfaces, nanostructures, capillary flow structures, enhanced evaporation surfaces, liquid film flow disruptors, microstructures to trip the condensate flow, microstructures to reduce the film thickness, and microstructures to remove the condensate film. 
     
     
         8 . The condenser of  claim 6 , wherein at least one of the heat transfer plate and the cover plate has a stepped surface to provide the decrease in cross-sectional flow area for the vapor in the vapor flow direction. 
     
     
         9 . The condenser of  claim 6 , wherein the flow channel comprises a cross-sectional area decreasing in the vapor flow direction. 
     
     
         10 . The condenser of  claim 6 , wherein the cover plate is a heat transfer plate. 
     
     
         11 . A combined evaporator and condenser unit, comprising:
 an evaporator flow channel having two open ends, optionally two sidewalls, and an evaporator cover plate enclosing the evaporator flow channel;
 an evaporator flow channel feed liquid inlet at a first end of the unit; 
 an evaporator flow channel feed liquid outlet at a second end of the unit; 
 optionally, an evaporator flow channel vapor flow inlet at the second end of the unit; 
 an evaporator vapor flow outlet at the first end of the flow channel; 
   a condenser flow channel having two open ends, optionally two sidewalls, and a condenser cover plate enclosing the condenser flow channel;
 a condenser flow channel vapor inlet at the first end of the unit; 
 a condenser liquid outlet at the second end of the unit; and 
 a common heat transfer plate disposed between the evaporator cover plate and the condenser cover plate, wherein an evaporator gap at the second end of the unit between the common heat transfer plate and the evaporator cover plate and a condenser gap at the second end of the unit between the common heat transfer plate and the cover plate are each independently in the range of from 1 mm to 200 mm and wherein an angle between the surface of the common heat transfer plate and the surface of the evaporator cover plate and an angle between the surface of the common heat transfer plate and the surface of the evaporator cover plate are each independently in the range of from 0.5 to 20 degrees.